Prostate cancer is the most prevalent type of cancer and it is the second highest contributor to cancer death among men in the U.S. A major issue in prostate cancer detection and therapy is that we currently have no method to reliably distinguish aggressive prostate cancer from non-aggressive prostate cancer. This leads to significant unnecessary suffering among prostate cancer patients. We hypothesize that specific glycoproteins or their glycosylation specifically altered in aggressive prostate cancer cells can be used as biomarkers to distinguish patients with aggressive from those with non-aggressive prostate cancer. We propose in four specific aims to develop novel glycoprotein biomarkers that can detect aggressive cancer in pre-surgical urine or biopsy tissues. In Aim 1, we will analyze urinary glycoproteins from patients with aggressive cancer and non-aggressive cancer using high throughput glycoproteomics and mass spectrometry to identify glycoproteins associated with aggressive prostate cancer. In Aim 2, we will validate the identified candidate urinary glycoproteins by targeted analysis of candidate glycoproteins from additional urine samples in independent testing sets of prostate cancer urine specimens from the EDRN network. In Aim 3, we will develop highly sensitive, specific, and high throughput ELISA or mass spectrometry based selective reaction monitoring assays as noninvasive urine tests using the glycoprotein biomarkers identified and validated from Aim 1 and Aim 2 and validate the performance of the tests for aggressive prostate cancer biomarkers. We will further determine the clinical utility of the validated tests to detect patients with aggressive prostate cancer in active surveillance program. In Aim 4, we will develop and optimize the immunohistochemistry assays for the glycoproteins associated aggressive prostate cancer tissues and validate these tissue glycoproteins using tissue microarrays. We will then further determine the clinical utility of the immunohistochemistry assays as biopsy based tissue tests for the early detection of patients with aggressive prostate cancer in active surveillance program. If successful, the identified and validated biomarkers will be tested by EDRN biomarker reference laboratory (BRL) and clinical validation center (CVC) in retrospective and prospective studies. Biomarkers capable of distinguishing aggressive from nonaggressive prostate cancer will allow men with aggressive prostate cancer to receive appropriate treatment earlier in the course of their diseases and prevent men with non- aggressive prostate cancer from overtreatment.